Home » Public Forums » GMCnet » [GMCnet] Any idea why my late 78 compressor discharge line is so tiny? .125 OD, .075 ID. REALLY.
| [GMCnet] Any idea why my late 78 compressor discharge line is so tiny? .125 OD, .075 ID. REALLY. [message #316759] |
Fri, 28 April 2017 21:37  |
BobDunahugh
Messages: 2465
Registered: October 2010
Location: Cedar Rapids, IA
Karma: 11
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( Looked at Barb's issue. Now mine.) That air line is stock from GM. That size air line comes out of the discharge side of the compressor to a solenoid valve. About 6". Then a standard air line out of the solenoid valve to the air bags. These late GMC's also have no air tank. I've heard that some owners have replace the 2 stock compressors with 2 ViAir compressors. So why can't I put in the two stock, 2 cyl units that I now have? Or any simple ways to test these compressors. I have a total of 6 of the late compressor. Bob Dunahugh Late 78 Royale
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| Re: [GMCnet] Any idea why my late 78 compressor discharge line is so tiny? .125 OD, .075 ID. REALLY. [message #316775 is a reply to message #316759] |
Sat, 29 April 2017 09:20  |
JohnS
Messages: 126
Registered: December 2014
Location: Vacaville, CA
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The lines are that size because that is what GM was using in the cars those units were designed for. No idea why they designed THOSE that way!
Those two compressors also incorporate the exhaust valves. If they are replaced, an exhaust valve for each side will need to be added. This change, or some other system, such as the wireless system, may be desirable, as those compressor/exhaust valve units are getting VERY expensive.
I have added those exhaust valves and installed Viair compressors on the 78 stretch. It goes up & down quickly! I considered a wireless system, but it's so heavy it needs more than 100psi to achieve full raise.
John Shutzbaugh, Vacaville, CA, ncserv@aol.com;
78 Buskirk stretch, "What were we thinking?"
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| Re: [GMCnet] Any idea why my late 78 compressor discharge line is so tiny? .125 OD, .075 ID. REALLY. [message #316776 is a reply to message #316775] |
Sat, 29 April 2017 10:07 |
Kosier
Messages: 834
Registered: February 2008
Karma: 1
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John,
If you're still using the OEM style air bags, you should consider going to
the Sully Bag system. If using one of the 4-bagger systems,
contact the bag manufacturer for a possibly higher capacity bag. Fatter
bags will let you carry the weight at a lower pressure, saving
you from problems caused by the higher pressure. At least, that's my honest
opinion.
Gary Kosier
77PB w/500Cad
Newark, Ohio
--------------------------------------------------
From: "John Shutzbaugh"
Sent: Saturday, April 29, 2017 10:20 AM
To:
Subject: Re: [GMCnet] Any idea why my late 78 compressor discharge line is
so tiny? .125 OD, .075 ID. REALLY.
> The lines are that size because that is what GM was using in the cars
> those units were designed for. No idea why they designed THOSE that way!
>
> Those two compressors also incorporate the exhaust valves. If they are
> replaced, an exhaust valve for each side will need to be added. This
> change,
> or some other system, such as the wireless system, may be desirable, as
> those compressor/exhaust valve units are getting VERY expensive.
>
> I have added those exhaust valves and installed Viair compressors on the
> 78 stretch. It goes up & down quickly! I considered a wireless system,
> but
> it's so heavy it needs more than 100psi to achieve full raise.
> --
> John Shutzbaugh, Vacaville, CA;
> 77 Eleganza, bought it new, can't blame PO, and
> 78 Buskirk stretch, "What were we thinking?"
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
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| Re: [GMCnet] Any idea why my late 78 compressor discharge line is so tiny? .125 OD, .075 ID. REALLY. [message #316783 is a reply to message #316776] |
Sat, 29 April 2017 11:26 |
JohnS
Messages: 126
Registered: December 2014
Location: Vacaville, CA
Karma: -2
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Thanks for the input, Gary,
I have considered the Sully bag system & have corresponded with Sully about the heavy stretch. He has reassured me that the bags are more than up to carrying the extra weight, and as you have pointed out, will do so at a significantly lower pressure.
The only reason I haven't changed is that the Sully bags allow almost an inch less height on full raise (and don't go down quite as far). Campground leveling is important to me. I have been trying to keep track of how many times we have needed full raise lately. Maybe I can make a decision based on that. Or carry more Winnebago blocks!
John Shutzbaugh, Vacaville, CA, ncserv@aol.com;
78 Buskirk stretch, "What were we thinking?"
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| Re: [GMCnet] Any idea why my late 78 compressor discharge line is so tiny? .125 OD, .075 ID. REALLY. [message #316837 is a reply to message #316790] |
Sun, 30 April 2017 12:50 |
sgltrac
Messages: 2797
Registered: April 2011
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I have found that the slight reduction in full raise is easily overcome by
taking a few extra minutes when selecting my final camp spot in order to
set the front wheels in a position where the front is slightly low compared
to the rear then drop the rear to make it level. This also lowers the entry
step making ingress and egress much more ergonomic. I almost never camp on
asphalt.
Sully
77 eleganza 2
Seattle
On Sat, Apr 29, 2017 at 10:46 AM John Shutzbaugh
wrote:
> Also, Sorry to all. Looks like I did some thread hijacking. Will be more
> careful in the future.
> --
> John Shutzbaugh, Vacaville, CA;
> 77 Eleganza, bought it new, can't blame PO, and
> 78 Buskirk stretch, "What were we thinking?"
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
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Sully
77 Royale basket case.
Future motorhome land speed record holder(bucket list)
Seattle, Wa.
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